1. Technical Field
The present invention generally relates to the field of clinical chemistry. More particularly, the present invention relates to a compact readhead and optical diagnostic system that uses ambient light to analyze the color change associated with one or more test areas on sample media following contact thereof with a liquid specimen, such as urine, saliva, blood serum or whole blood.
2. Background Information
Throughout this application, various patents are referred to by an identifying citation. The disclosures of the patents referenced in this application are hereby incorporated by reference into the present disclosure.
Sample media such as reagent test strips are widely used in the field of clinical chemistry. A test strip usually has one or more test areas spaced along the length thereof, with each test area being capable of undergoing a color change in response to contact with a liquid specimen. The liquid specimen usually contains one or more constituents or properties of interest. The presence and concentrations of these constituents or properties are determinable by an analysis of the color changes undergone by the test strip. Usually, this analysis involves a color comparison between the test area or test pad and a color standard or scale. In this way, reagent test strips assist physicians in diagnosing the existence of diseases and other health problems.
Color comparisons made with the naked eye can lead to imprecise measurement. Today, strip reading instruments exist that employ reflectance photometry for reading test strip color changes. These instruments accurately determine the color change of a test strip within a particular wavelength range or bandwidth. Examples of such instruments include those sold under the CLINITEK® trademark by Siemens Medical Solutions Diagnostics (Tarrytown, N.Y.) and/or as disclosed in U.S. Pat. Nos. 5,408,535 and 5,877,863 (the '863 patent), both of which are fully incorporated by reference herein. These instruments are typically used to detect colors associated with a urine specimen on a MULTISTIX® (Siemens) reagent strip.
Another strip reading instrument utilizing reflectance photometry to read multiple test strips is disclosed in U.S. Pat. No. 5,055,261. An operator sequentially places test strips in a loading area. An arm orients the test strips on rails extending from the loading area to one or more reading stations employing readheads.
A common aspect of these instruments is that their relative size and complexity, particularly with respect to those utilizing automated test pad transport systems, render them relatively bulky and difficult to transport. Rather, these devices tend to be installed at a dedicated testing center or laboratory, where samples are aggregated and tested in bulk. Unfortunately, such aggregation of samples from multiple patients presents opportunities for error due to mislabeling of the samples and/or the test results. Moreover, in many instances, the time required for transporting the samples to and from the processing center, and for testing and recording the results, may be problematic.
A portable diagnostic device is described in U.S. Provisional Patent Application Ser. No. 60/550,811, entitled Handheld Optical Diagnostic Device Having Image System Array, filed Mar. 5, 2004, which is fully incorporated herein by reference. This device advantageously provides a portable means for analyzing the aforementioned reagent strips.
Other portable diagnostic devices include the Clearblue™ Digital Pregnancy Test device (Unipath Limited, UK) and the glucose test system disclosed in U.S. Pat. No. 6,055,060. These are generally single test devices, i.e., used to test for single analytes, such as the hCG hormone (pregnancy) or glucose. As such, these devices may be optimized for relatively narrow spectral (color) detection ranges, such as blue in the case of the Clearblue™ tester, and yellow/green for the glucose test system. Moreover, even with the relative simplicities inherent with such single analyte testing environments, these devices tend to utilize relatively complex readhead systems that may be labor intensive to manufacture.
In addition, most of the foregoing approaches rely on a relatively complex illumination scheme to provide carefully controlled levels and wavelengths of lighting in order to provide accurate color determination.
Another, relatively simple, portable imaging device has been disclosed by Takao Someya and Takayasu Sakurai, of the University of Tokyo, in “Opto & Laser Europe”, February 2005, pages 22-23). This device is a mechanically flexible film scanner configured to capture black and white images from non-flat surfaces, such as of labels affixed to bottles. Illumination is provided by ambient lighting, which eliminates the complexity associated with the aforementioned carefully controlled on-board illumination. However, Someya, et al. teach that their device is capable of only black and white imaging, and thus is not capable of the accurate color determination needed in the field of medical diagnostic imaging. Moreover, Someya et al. disclose a relatively large sensor density, which would be expected to increase with the stated goal of increasing image resolution from the current 36 dots per inch (dpi) to a goal of 600 dpi. Such a large sensor density, however, leaves relatively small gaps therebetween, through which ambient light may pass to illuminate the label. This configuration therefore tends to create shadows on the label that would militate against using this approach to obtain the accurate color measurements that would be required for sophisticated medical diagnostic applications.
A need therefore exists for an inexpensive, portable, and mechanically rugged readhead and diagnostic testing device that enables a care provider to obtain quick and accurate test results for a range of analytes without the need for sending sample media to a remote testing center for processing. A need also exists for a readhead and portable diagnostic testing device of relatively low mechanical and electronic complexity, to provide for simplified manufacturability, and low power consumption to enable extended operation using a portable power supply.